U.S. patent application number 12/682280 was filed with the patent office on 2010-09-16 for alkylation process using a catalyst comprising rare earth containing zeolites and reduced amount of noble metal.
This patent application is currently assigned to Albemarle Netherlands, BV. Invention is credited to Mark Hendrikus Harte, Emanuel Hermanus Van Broekhoven.
Application Number | 20100234661 12/682280 |
Document ID | / |
Family ID | 40148618 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100234661 |
Kind Code |
A1 |
Van Broekhoven; Emanuel Hermanus ;
et al. |
September 16, 2010 |
ALKYLATION PROCESS USING A CATALYST COMPRISING RARE EARTH
CONTAINING ZEOLITES AND REDUCED AMOUNT OF NOBLE METAL
Abstract
An improved alkylation process utilizing a solid-acid catalyst
comprising a rare earth containing zeolite and a hydrogenation
metal is disclosed.
Inventors: |
Van Broekhoven; Emanuel
Hermanus; (Monnickendam, NL) ; Harte; Mark
Hendrikus; (Zaandam, NL) |
Correspondence
Address: |
ALBEMARLE CORPORATION;PATENT DEPARTMENT
451 FLORIDA STREET
BATON ROUGE
LA
70801
US
|
Assignee: |
Albemarle Netherlands, BV
Amsterdam
NL
|
Family ID: |
40148618 |
Appl. No.: |
12/682280 |
Filed: |
October 7, 2008 |
PCT Filed: |
October 7, 2008 |
PCT NO: |
PCT/EP08/63409 |
371 Date: |
April 9, 2010 |
Current U.S.
Class: |
585/722 |
Current CPC
Class: |
B01J 38/58 20130101;
B01J 29/126 20130101; B01J 2229/36 20130101; C07C 2/58 20130101;
B01J 29/06 20130101; C07C 2523/10 20130101; C07C 2523/44 20130101;
C07C 2529/18 20130101; C07C 2523/42 20130101; B01J 2229/186
20130101; C07C 2521/04 20130101; B01J 2229/24 20130101; C07C
2529/70 20130101; C07C 2/58 20130101; B01J 2229/16 20130101; C07C
2529/08 20130101; B01J 38/56 20130101; Y02P 20/584 20151101; C07C
9/16 20130101 |
Class at
Publication: |
585/722 |
International
Class: |
C07C 2/58 20060101
C07C002/58 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2007 |
US |
60980616 |
Claims
1. A process for alkylating hydrocarbons wherein an alkylatable
organic compound is reacted with an alkylation agent to form an
alkylate in the presence of a catalyst comprising between about
0.15 wt % and 0.25 wt % of at least one noble metal and a
rare-earth containing solid acid constituent, with the catalyst
being subjected intermittently to a regeneration step by being
contacted with a feed containing a saturated hydrocarbon and
hydrogen, said regeneration being carried out at 90% or less of the
active cycle of the catalyst, with the active cycle of the catalyst
being defined as the time from the start of the feeding of the
alkylation agent to the moment when, in comparison with the
entrance of the catalyst-containing reactor section, 20% of the
alkylation agent leaves the catalyst-containing reactor section
without being converted, not counting isomerization inside the
molecule, wherein said catalyst is regenerated before there is any
substantial decrease of activity of said catalyst.
2. The process of claim 1 wherein the alkylatable organic compound
is isobutane and the alkylation agent comprises C3-C5 alkenes.
3. The process of claim 2 wherein the alkylation agent is butene or
a mixture of butenes.
4. The process of claim 1 wherein the at least one noble metal is
disposed on a carrier comprising about 2 to about 98 wt % matrix
material comprising alumina and the balance is the rare-earth
containing solid acid constituent.
5. The process of claim 1 wherein the solid acid constituent is a
faujasite
6. The process of claim 5 wherein the solid acid constituent is
prepared by a process comprising the steps of: preparing a sodium
zeolite, ion exchanging the sodium zeolite with NH.sub.4.sup.+--
and rare earth ions to reduce Na.sub.2O to about 4 to about 5 wt %,
steaming the zeolite at about 400 to about 500.degree. C. such that
a.sub.0 ranges from about 24.62 to about 24.70 .ANG., ion
exchanging with NH.sub.4.sup.+ ions to reduce Na.sub.2O to about
0.3 to about 0.9 wt %, and drying.
7. The process of claim 6 wherein the bulk SAR of the product
zeolite ranges from about 6 to about 12.
8. The process of claim 1 wherein the noble metal is platinum,
palladium, or a mixture thereof.
9. The process of claim 1 wherein the rare earth is lanthanum.
10. The process of claim 1 wherein the catalyst is periodically
subjected to a high temperature regeneration with hydrogen in the
gas phase.
11. The process of claim 1 wherein the catalyst is prepared by a)
calcining solid acid-containing particles at a temperature in the
range of about 400 to about 575.degree. C., b) incorporating a
Group VIII noble metal into the calcined particles to form noble
metal-containing particles, and c) calcining the noble
metal-containing particles at a temperature in the range of about
350 to about 600.degree. C.
12. The process according to claim 11 wherein the catalyst further
comprises from about 1.5 to about 6 wt % of water, measured as the
loss on ignition at 600.degree. C.
13. The process according to claim 12 wherein the catalyst is
prepared by adding water to a dry catalyst comprising solid acid
and at least one noble metal before use in the alkylation
process.
14. The process according to claim 1 wherein the alkylation process
is started using a catalyst comprising less than about 1.5 wt %
water and wherein water is added to the catalyst during the
alkylation process.
Description
[0001] The term alkylation refers to the reaction of an alkylatable
compound, such as an aromatic or saturated hydrocarbon, with an
alkylation agent, such as an olefin. The reaction is of interest
because it makes it possible to obtain, through the alkylation of
e.g. isobutane with an olefin containing 2-6 carbon atoms, an
alkylate which has a high octane number and which boils in the
gasoline range. Unlike gasoline obtained by cracking heavier
petroleum fractions such as vacuum gas oil and atmospheric residue,
gasoline obtained by alkylation is essentially free of contaminants
such as sulfur and nitrogen and thus has clean burning
characteristics. Its high anti-knock properties, represented by the
high octane number, lessen the need to add environmentally harmful
anti-knock compounds such as aromatics or lead. Also, unlike
gasoline obtained by reforming naphtha or by cracking heavier
petroleum fractions, alkylate contains few if any aromatics or
olefins, which offers further environmental advantages.
[0002] The alkylation reaction is acid-catalyzed. Conventional
alkylation process equipment makes use of liquid acid catalysts
such as sulfuric acid and hydrofluoric acid. The use of such liquid
acid catalysts is attended with a wide range of problems. For
instance, sulfuric acid and hydrofluoric acid are both highly
corrosive, so that the equipment used has to meet severe service
requirements. Since the presence of highly corrosive materials in
the resulting fuel is objectionable, the remaining acid must be
removed from the alkylate. Also, because of the liquid phase
separations that must be carried out, the process is complicated
and expensive. In addition, there is always the risk that toxic
substances such as hydrogen fluoride will be emitted to the
environment.
[0003] The present invention provides an improved alkylation
process utilizing a solid-acid catalyst comprising a rare earth
containing zeolite and reduced amounts of noble metal as compared
to the prior art.
[0004] The water content of the catalyst ranges from about 1.5 wt %
to about 6 wt %, in one embodiment it ranges from about 1.8 wt % to
about 4 wt %, and in another embodiment it ranges from about 2 wt %
to about 3 wt %. The water content of the catalyst is defined as
its water content during use in the alkylation process and is
measured by determining the weight loss upon heating the catalyst
for two hours at 600.degree. C. (Loss on Ignition, or LOI 600).
[0005] The catalyst comprises a hydrogenation metal. Examples of
suitable hydrogenation metals are the transition metals, such as
metals of Group VIII of the Periodic Table, and mixtures thereof.
Among these, the noble metals of Group VIII of the Periodic Table,
particularly platinum, palladium, and mixtures thereof, are
especially preferred. However, noble metals have an economic
disadvantage due to their high costs. The amount of hydrogenation
metal present in the catalyst will depend on its nature. When the
hydrogenation metal is a noble metal of Group VIII of the Periodic
Table, the catalyst may contain in the range of about 0.01 to about
2 wt % of the metal. It has been found that by employing rare earth
or rare earth mixtures to modify the solid acid component of the
catalyst, as described below, the amount of noble metal may be
optimised. In one embodiment, the optimum amount of noble metal
ranges between about 0.10 wt % and about 0.35 wt %. In another, the
optimum amount of noble metal ranges between about 0.15 wt % and
0.30 wt %. In yet another, the optimum amount of noble metal ranges
between about 0.15 wt % and 0.25 wt %.
[0006] The catalyst further comprises a solid acid. Examples of
solid acids are zeolites such as zeolite beta, MCM-22, MCM-36,
mordenite, faujasites such as X-zeolites and Y-zeolites, including
H--Y-zeolites and USY-zeolites, non-zeolitic solid acids such as
silica-alumina, sulfated oxides such as sulfated oxides of
zirconium, titanium, or tin, mixed oxides of zirconium, molybdenum,
tungsten, phosphorus, etc., and chlorinated aluminium oxides or
clays. Preferred solid acids are zeolites, including mordenite,
zeolite beta, faujasites such as X-zeolites and Y-zeolites,
including HY-zeolites and USY-zeolites. Mixtures of solid acids can
also be employed. In one embodiment the solid acid is a faujasite
with a unit cell size (a.sub.0) of 24.72 to about 25.00 angstroms,
in another embodiment the solid acid is Y-zeolite with a unit cell
size of 24.34-24.72 angstroms, while in another the solid acid is
Y-zeolite with a unit cell size of 24.42-24.56 angstroms. In yet
another embodiment the solid acid is Y-zeolite with a unit cell
size of 24.56-24.72 angstroms.
[0007] The solid acid component of the catalyst comprises rare
earth or rare earth mixtures, i.e., elements chosen from the
lanthanide series. In one embodiment, rare earth ranges from about
0.5 wt % to about 32 wt %. In another, rare earth ranges from about
2 wt % to about 9 wt %. In yet another, rare earth ranges from
about 4 wt % to about 6 wt %.
[0008] The rare earth element(s) may be exchanged into the solid
acid component by conventional means. In one embodiment, the solid
acid component is a lanthanum exchanged Y-zeolite.
[0009] The catalyst may additionally comprise a matrix material.
Examples of suitable matrix materials are alumina, silica, titania,
zirconia, clays, and mixtures thereof. Matrix materials comprising
alumina are generally preferred. In one embodiment, the catalyst
comprises about 2 wt % to about 98 wt % of the solid acid and about
98 wt % to about 2 wt % of the matrix material, based on the total
weight of the solid acid and the matrix material present in the
catalyst. In another embodiment, the catalyst comprises about 10 wt
% to about 90 wt % of the solid acid and about 90 wt % to about 10
wt % of the matrix material, based on the total weight of the solid
acid and the matrix material contained in the catalyst. In another
embodiment, the catalyst comprises about 10 wt % to about 80 wt %
of matrix material and balance solid acid. In yet another
embodiment, the catalyst comprises about 10 wt % to about 40 wt %
of the matrix material and balance solid acid, based on the total
weight of the solid acid and the matrix material contained in the
catalyst.
[0010] The catalyst preferably contains no halogen component.
[0011] In one embodiment, the catalyst comprises catalyst particles
wherein the ratio between (i) the volume in catalyst pores with a
diameter of about 40 to about 8,000 nm (herein defined as
"macropores") and (ii) the specific length of the catalyst
particles is in the range of about 0.01 to about 0.90 ml/(g*mm),
and wherein the catalyst has a total pore volume of at least 0.20
ml/g.
[0012] The specific length of a catalyst particle is defined as the
ratio between the geometric volume and the geometric surface of the
solid part of this catalyst particle. The determination of the
geometric volume and the geometric surface is known to the person
skilled in the art and can be carried out, e.g., as described in DE
2354558.
[0013] The macropore volume as well as the total pore volume is
determined via mercury intrusion on the basis of the Washburn
equation covering pores with a diameter of 3.6-8,000 nm.
[0014] In one embodiment, the ratio between the volume in
macropores and the specific length is above about 0.20 ml/(g*mm),
and in another above about 0.30 ml/(g*mm). In yet another
embodiment, the ratio is above about 0.40 ml/(g*mm), but below
about 0.80 ml/(g*mm).
[0015] In one embodiment, the catalyst has a total pore volume of
at least about 0.23 ml/g and in another at least about 0.25
ml/g.
[0016] In one embodiment, the catalyst particles have a specific
length of at least about 0.10 mm, in another at least about 0.16
mm, and in yet another at least about 0.20 mm. In one embodiment,
the upper limit of the specific length lies at about 2.0 mm, in
another at about 1.0 mm, and in yet another at about 0.6 mm.
[0017] The pore volume in macropores in one embodiment of the
catalyst is at least about 0.05 ml/g, in another at least about
0.08 ml/g. In one embodiment, the upper limit of the pore volume in
macropores is below about 0.30 ml/g, in another below about 0.25
ml/g.
[0018] The particles of the catalyst can have many different
shapes, including spheres, cylinders, rings, and symmetric or
asymmetric polylobes, for instance tri- and quadrulobes.
[0019] In one embodiment, the catalyst particles have an average
particle diameter of at least about 0.5 mm, in another embodiment
at least about 0.8 mm, and in yet another embodiment at least about
1.0 mm. In one embodiment, the upper limit of the average particle
diameter lies at about 10.0 mm, in another at about 5.0 mm, and in
yet another embodiment at about 3.0 mm.
[0020] The catalyst used in the process according to the invention
is prepared by adjusting the water content. For example, the solid
acid constituent may be mixed with a matrix material, to form
carrier particles, followed by calcination of the particles. The
hydrogenating function may, e.g., be incorporated into the catalyst
composition by impregnating the carrier particles with a solution
of a hydrogenation metal component. After impregnation the catalyst
may be calcined.
[0021] In one embodiment, the catalyst is reduced at a temperature
in the range of about 200 to about 500.degree. C. in a reducing gas
such as hydrogen. In another embodiment, the catalyst is reduced at
a temperature in the range of about 250 to about 350.degree. C. The
reduction can be performed before adjustment of the water content,
after addition of water to the catalyst and/or by using reduction
as a way to adjust the water content. In one embodiment, the
reduction is performed before adjustment of the water content. In
another, the reduction is performed after drying the catalyst in a
dry, non-reducing gas (such as nitrogen, helium, air, and the
like).
[0022] The water content of the catalyst can be adjusted by various
methods as described in PCT/EP2005/000929, which is incorporated by
reference in its entirety. Such methods are exemplified below as
methods 1, 2, and 3.
[0023] Method 1 involves increasing the LOI of a catalyst by
exposing the catalyst to water. This can be achieved by exposing
the catalyst to a water-containing atmosphere, e.g., air at ambient
conditions. Embodiments of this method include exposing a reduced
catalyst to water until the desired LOI is reached, exposing an
unreduced catalyst to water until an LOI above the desired level is
reached, followed by reduction of the catalyst, thereby decreasing
the LOI to the desired level, exposing a reduced catalyst to water
until an LOI above the desired level is reached, followed by
treatment of the catalyst in either an inert or a reducing
atmosphere, thereby decreasing the LOI to the desired level, and
reducing the catalyst in a hydrogen and water-containing
atmosphere.
[0024] Method 2 involves decreasing the LOI of an existing catalyst
to the desired level by reducing an unreduced catalyst with an LOI
above the desired level.
[0025] Method 3 involves in-situ water addition by starting the
alkylation process with a catalyst having an LOI below the desired
level and adding water to the alkylation unit during processing,
for instance by adding water to the hydrocarbon feed, by
regenerating the catalyst in a water-containing atmosphere and/or
by exposing the regenerated catalyst to a water-containing
atmosphere.
[0026] A combination of two or more of the above methods may also
be employed.
[0027] The hydrocarbon to be alkylated in the alkylation process is
a branched saturated hydrocarbon such as an isoalkane having 4-10
carbon atoms. Examples are isobutane, isopentane, isohexane or
mixtures thereof. The alkylation agent is an olefin or mixture of
olefins having 2-10 carbon atoms. In one embodiment, the alkylation
process consists of the alkylation of isobutane with butenes.
[0028] As will be evident to the skilled person, the alkylation
process can take any suitable form, including fluidized bed
processes, slurry processes, and fixed bed processes. The process
can be carried out in a number of beds and/or reactors, each with
separate addition of alkylation agent if desirable. In such a case,
the process of the invention can be carried out in each separate
bed or reactor.
[0029] As mentioned above, water may be added during the process in
order to increase the LOI of the catalyst to the desired level.
This water can be introduced during the alkylation reaction via,
e.g., the hydrocarbon feed or the feed of alkylation agent.
Alternatively, the catalyst can be hydrated by using a
water-containing atmosphere during the optional (mild) regeneration
steps described below, or by contacting the catalyst with water in
a separate intermediate hydration step. Similar procedures can be
applied to rehydrate the catalyst after its LOI has decreased
during processing (i.e. during the alkylation reaction and/or
regeneration).
[0030] Suitable process conditions are known to the skilled person.
Preferably, an alkylation process as disclosed in WO 98/23560 is
applied. The process conditions applied in the present process are
summarized in the following Table:
TABLE-US-00001 Molar ratio of Temperature range Pressure range
hydrocarbon to [.degree. C.] [bar] alkylation agent Preferred
-40-250 1-100 5:1-5,000:1 More preferred 20-150 5-40 50:1-1,000:1
Most preferred 65-95 15-30 150:1-750:1
[0031] Optionally, the catalyst may be subjected to a
high-temperature regeneration with hydrogen in the gas phase. This
high-temperature regeneration may be carried out at a temperature
of at least about 150.degree. C., in one embodiment regeneration is
carried out at about 150.degree. to about 600.degree. C., and
another at about 200.degree. to about 400.degree. C. For details of
this regeneration procedure, reference is made to WO 98/23560, and
in particular to page 4, lines 12-19, which is herein incorporated
in its entirety by reference. The high-temperature regeneration can
be applied periodically during the alkylation process. If as a
result of high-temperature regeneration the water content of the
catalyst has decreased to below the desired level, the catalyst may
be rehydrated during the process in the ways described above.
[0032] In addition to the high-temperature regeneration treatment,
a milder regeneration may be applied during the alkylation process,
such as described in WO 98/23560, in particular page 9, line 13
through page 13, line 2, which is herein incorporated in its
entirety by reference. During the alkylation process, the catalyst
may be subjected intermittently to a regeneration step by being
contacted with a feed containing a hydrocarbon and hydrogen, with
said regeneration being carried out at about 90% or less of the
active cycle of the catalyst in one embodiment, at 60% or less in
another embodiment, at 20% or less in yet another embodiment, and
at 10% or less in another embodiment. The active cycle of the
catalyst is defined herein as the time from the start of the
feeding of the alkylation agent to the moment when, in comparison
with the alkylation agent added to the catalyst-containing reactor
section, 20% of the alkylation agent leaves the catalyst-containing
reactor section without being converted, not counting isomerization
inside the molecule.
[0033] The catalyst of the present invention may be prepared by a
process comprising the steps of a) calcining solid acid-containing
particles at a temperature in the range of about 400 to about
575.degree. C.; b) incorporating a Group VIII noble metal into the
calcined particles to form noble metal-containing particles; and c)
calcining the noble metal-containing particles at a temperature in
the range of about 350 to about 600.degree. C.
[0034] Performance in alkylation reactions of catalysts of the
present invention can be further improved if the calcination steps
before and after incorporation of the hydrogenation component are
both conducted in a specific temperature window.
[0035] The solid acid-containing particles are calcined in step a)
at a temperature in the range of about 400 to about 575.degree. C.,
in another embodiment in the range of about 450 to about
550.degree. C., and in yet another embodiment in the range of about
460 to about 500.degree. C. The heating rate ranges from about 0.1
to about 100.degree. C./min, and in one embodiment from about
0.5.degree. C. to about 50.degree. C./min, and in another
embodiment from about 1 to about 30.degree. C./min. Calcination is
conducted for about 0.01 to about 10 hrs, and in one embodiment for
about 0.1 to about 5 hrs, and in another embodiment for about 0.5
to about 2 hrs. It may be conducted in an air and/or inert gas
(e.g. nitrogen) flow. In one embodiment this gas flow is dry.
[0036] In another embodiment, the solid acid-containing particles
are dried before being calcined. This drying may be conducted at a
temperature of about 110 to about 150.degree. C.
[0037] The calcination can be performed in any equipment, such as a
fixed bed reactor, a fluidized bed calciner, and a rotating tube
calciner.
[0038] A Group VIII noble metal or metals is then incorporated into
the calcined solid acid-containing particles in step b). In one
embodiment, this is preformed by impregnation or competitive ion
exchange of the solid acid-containing particles using a solution
comprising Group VIII noble metal ions and/or their complexes and
(optionally) NH4+ ions. In another embodiment, the Group VIII noble
metals are platinum, palladium, and combinations thereof. In yet
another embodiment, at least one of the Group VIII noble metals is
platinum. Suitable Group VIII noble metal salts include nitrates,
chlorides, and ammonium nitrates of the noble metals or their
complexes (e.g. NH3 complexes).
[0039] The resulting noble metal-containing particles are then
calcined at a temperature in the range of 350-600.degree. C. in
step c). In one embodiment, the particles are calcined at about 400
to about 550.degree. C., and in another from about 450 to about
500.degree. C. This temperature is may be reached by heating the
particles by about 0.1 to about 100.degree. C./min to the desired
final value between about 350 and about 600.degree. C. In one
embodiment, they are heated by about 0.5 to about 50.degree.
C./min, in another by about 1 to about 30.degree. C./min.
Calcination may be conducted for about 0.01 to about 10 hrs, and in
one embodiment for about 0.1 to about 5 hrs, and in another for
about 0.5 to about 2 hrs. Calcination may be conducted in an air
and/or inert gas (e.g. nitrogen) flow. In one embodiment this gas
flow is dry.
[0040] Optionally, a separate drying step is applied between steps
(b) and (c). Alternatively, the noble metal-containing particles
are dried during the calcination step. Also optionally, a dwell of
about 15-120 minutes is introduced at a temperature of about 200 to
about 250.degree. C.
[0041] After calcination step (c), the resulting catalyst particles
may be reduced at a temperature range of about 200 to about
500.degree. C., in one embodiment form about 250 to about
350.degree. C., in a reducing gas such as hydrogen.
EXAMPLES
Performance of Catalyst Comprising Rare Earth Ions and Reduced
Concentration of Noble Metal
[0042] The reference standard Y-zeolite without rare earth ions was
prepared via a conventional route, i.e., sodium-Y-zeolite (NaY) was
prepared (SAR 5.5, Na.sub.2O about 13 wt %) followed by ion
exchange with NH.sub.4.sup.+-ions (remaining Na.sub.2O typically
about 4.2 wt %), steaming at about 575 to about 625.degree. C.
resulting in an a.sub.0 of about 24.53-24.57 .ANG., a second ion
exchange with NH.sub.4.sup.+-ions (remaining Na.sub.2O typically
1.0 wt %), further steaming at about 500 to about 550.degree. C.
resulting in an a.sub.0 of about 24.44-24.52 .ANG., acid leaching
with either H.sub.2SO.sub.4 or HCl in the absence of
NH.sub.4.sup.+-ions at a temperature of about 80.degree. C. to
increase the bulk-SAR (SAR is defined as the ratio of SiO2 and
Al2O3 (mol/mol) present in the zeolite material) from about 6 to
about 12 (Na.sub.2O drops to about 0.2 wt %), and drying.
[0043] The zeolite of the invention is prepared according to
similar procedures, however NH.sub.4.sup.+-- as well as rare earth
ions are used in the first exchange step and the steaming
temperature is reduced to about 400 to about 500.degree. C. At this
low steaming temperature, less non-framework alumina is formed and
acid leaching is not required. So after the first steam treatment,
only exchange with NH.sub.4.sup.+-ions is required and then the
zeolite is dried. However, multiple steaming and ion exchange with
NH.sub.4.sup.+-ions steps may be employed if required to achieve
appropriate SAR, a.sub.0, and Na.sub.2O content. In one embodiment,
Na.sub.2O ranges from about 0.2 to about 0.9 wt %, SAR ranges from
about 6 to about 8, a.sub.0 ranges from about 24.58-24.72 angstrom
and rare earth ranges from about 2 to about 9 wt %.
[0044] In other embodiments Na.sub.2O ranges from about 0.3 to
about 0.5 wt %, SAR ranges from about 6 to about 7, a.sub.0 ranges
from about 24.62-24.70 angstrom and rare earth ranges from about 4
to about 6 wt %.
[0045] The tested alkylation catalysts had the following
compositions and properties: from about 60 to about 80% of the
above-described zeolite, from about 20 to about 40% alumina, from
about 0.05 to about 0.35% platinum, the average particle length
ranges from about 2 to about 6 mm, the average length/diameter
ratio ranges from about 1 to about 7.5, the particle diameter
ranges from about 0.5 to about 3 mm, and the side crush strength
ranges from about 1.5 to about 10 lbs/mm.
General Test Procedure:
[0046] A fixed-bed recycle reactor as described in WO 9823560,
which is herein incorporated by reference in its entirety, having a
diameter of 2 cm was filled with a 1:1 volume/volume mixture of
38.6 grams of catalyst extrudates (on dry basis, i.e. the actual
weight corrected for the water content) and carborundum particles
(60 mesh). At the center of the reactor tube a thermocouple of 6 mm
in diameter was arranged. The reactor was flushed with dry nitrogen
for 30 minutes (21 NI/hour). Next, the system was tested for
leakages at elevated pressure, after which the pressure was set to
21 bar and the nitrogen flow to 21 NI/hour. The reactor temperature
was then raised to 275.degree. C. at a rate of 1.degree. C./min, at
275.degree. C. nitrogen was replaced by dry hydrogen and the
catalyst was reduced at 275.degree. C.
[0047] Alternatively, in case of high temperature regeneration of
the same catalyst sample between runs, after draining and flushing
the reactor with hydrogen to remove hydrocarbons while maintaining
the alkylation reaction temperature, hydrogen flow was set to 21
NI/hour and the reactor temperature was then raised to 275.degree.
C. at a rate of 1.degree. C./min, and the catalyst was regenerated
at 275.degree. C.
[0048] After 2 hours, the reactor temperature was lowered to the
reaction temperature. During cooling down water was added to the
hydrogen flow to obtain an LOI of the catalyst of about 2-3 wt %
(the LOI of the catalyst is defined as the catalyst's weight loss
after heating for two hours at 600.degree. C.).
[0049] The hydrogen stream was stopped with the attaining of the
reaction temperature. Isobutane containing about 2.5-3 wt %
alkylate (added to accelerate deactivation rate, composition of the
alkylate added is similar to alkylate produced by the process at
the conditions described) and about 1 mol % of dissolved hydrogen
was supplied to the reactor at a rate of about 4,000 grams/hour.
(Note in the case of the catalysts without rare earth the test
conditions were less severe, since no alkylate was added to the
isobutane). About 95-98% of the isobutane/alkylate mixture was fed
back to the reactor. About 2-5% was drained off for analysis. Such
an amount of isobutane/alkylate mixture was supplied to the reactor
as to ensure a constant quantity of liquid in the system. When the
system had stabilized, hydrogen addition was stopped and such an
amount of cis-2-butene was added to it as to give a
cis-2-butene-WHSV of about 0.2 in the case of the rare earth
containing samples and of about 0.13 in the case of the samples
without rare earth. The overall rate of flow of liquid in the
system was maintained at about 4,000 g/h. The weight ratio of
isobutane to cis-2-butene at the reactor inlet was about 500-600 in
the case of the samples with rare earth and about 700-800 in the
case of the samples without rare earth. The pressure in the reactor
amounted to about 21 bar. Total alkylate concentration of the
hydrocarbon recycle flow (from added and produced alkylate) was
maintained at about 6.5-7.5 wt % during the test by controlling the
drain off flow to analyses. Note in the case of the samples without
rare earth the alkylate concentration was about 2.5-3.5 wt %.
[0050] Each time after 1 hour of reaction, the catalyst was
regenerated by being washed with isobutane/alkylate mixture for 5
minutes, followed by 50 minutes of regeneration through being
contacted with a solution of 1 mole % of H2 in isobutane/alkylate
mixture, and then being washed with isobutane/alkylate mixture for
another 5 minutes (total washing and regeneration time 1 hour).
After this washing step, alkylation was started again.
[0051] The temperature during the washing steps, the regeneration
step, and the reaction step was the same.
[0052] The process was conducted as above and the catalytic
performance was measured as a function of time.
[0053] The performance was characterized by the olefin conversion
per reactor pass and the research octane number (RON). The RON was
determined as described on pages 13 and 14 of WO 9823560, the only
exception being that the RON contribution of total C9+(excl.
2,2,5-trimethylhexane) was estimated to be 84 instead of 90.
[0054] Olefin conversion per reactor pass is the weight fraction
(as a percentage) of olefins that is converted between the
inlet--and the outlet of the catalyst bed, not counting
isomerization within the olefin molecules. A high conversion of
olefin is desired to reduce secondary reactions leading to
deactivation of the catalyst. Therefore, all catalysts were
compared at initial conversion levels that were higher than 95%. In
the case of the test conditions of the catalysts with rare earth
the temperature had to be controlled at about 75.degree. C. to
obtain these conversion levels. In the case of the much less severe
test conditions of the catalysts without rare earth the temperature
was controlled at about 55.degree. C.
[0055] FIG. 1 shows the effect on RON of the catalyst formulations
of the present invention. The platinum content was varied between
0.05 wt % to 0.35 wt %. All catalyst tested comprised about 70 wt %
zeolite. The catalysts contain about 5 wt % rare earth. The
calculated weighted hourly space velocity was about 0.2 and the
calculated isobutane to olefin ratio of the isobutane and olefin
fed to the reactor was about 24. The results show that RON varies
little above a Pt content of about 0.15-0.20 wt %. Below about 0.15
wt % Pt content a more significant reduction of RON is
observed.
[0056] FIG. 2 shows that when noble metal content of a catalyst
comprising zeolite that does not contain rare earth is varied,
catalyst performance deteriorates much faster with decreasing noble
metal content and results in an optimum noble metal content of
about 0.35 wt %, which is much higher than that required when the
zeolite comprises rare earth. The calculated weighted hourly space
velocity was about 0.13 and the calculated isobutane to olefin
ratio of the isobutane and olefin fed to the reactor was about
30.
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